Pattern Evoked Cortical Potentials and Automated Perimetry in Chronic Glaucoma

Abstract

Chronic glaucoma causes visual field defects and in some cases an increase in the latency of pattern evoked visual potentials (P E P). To assess the contribution of field defects to the latency increase in PEP we have reexamined 16 glaucoma patients out of a group of 27 whose PEP had been recorded two years before (Huber and Wagner 1978). PEP measurements and visual fields measured by automated static perimetry (Octopus) where compared. A significant increase in PEP latency could only be demonstrated in the presence of a relative central scotoma. The depth of the relative scotoma is related to the increase in latency. Peripheral field defects do not affect the PEP latency as a small central island of vision with normal sensitivity is sufficient to produce a normal PEP. A large visual field with reduced central sensitivity can however result in a large latency increase. Over a period of two years the shape of the individual PEP is constant. The latency increase in glaucoma thus represents a differential diagnosis of increased PEP latency in the context of neurological diseases. PEPs are not an adequate method for the detection of early glaucoma as the sensitivity of the visual field’s center can be unaffected for a long time in this disease.